Thread gripping device in circular knitting machines for hosiery or the like

ABSTRACT

A device for gripping thread in circular hosiery knitting machines comprising a supporting element fixable to the structure of the machine supporting the thread guides proximate to a drop or feed, above the needle cylinder and proximate to the needle work area, that bears at least one elastic lamina element and a thread locking lever pivoted to the supporting element and rotatable scissor-like with respect to the elastic lamina element to catch the thread with a grip portion between the locking lever and the elastic lamina element. The thread grip portion of the locking lever has two opposite shoulders that delimit bilaterally movement of the thread toward or away from the axis of the needle cylinder.

BACKGROUND OF THE INVENTION

In circular knitting machines for hosiery or the like, at the end of aknitting process performed with the thread dispensed by a correspondingthread guide at a feed or drop of the machine, the thread guide is movedinto a position in which it prevents the needles from engaging thethread and the thread is cut.

The portion of thread that lies between the corresponding thread guideand the end formed by the cut is kept in a position that allows toresume knitting with that thread.

Generally, thread guides are arranged around the needle cylinder justabove its upper end, and in order to prevent the needles from engagingthe thread the thread dispensing end of said thread guides is raised.

At the upper end of the needle cylinder, just below the dispensing endof the thread guides, when such end is lowered to feed the thread to theneedles, there is a circular cutter, which is arranged coaxially to theneedle cylinder and has a slightly smaller diameter than the cylindricalsurface traced by the needles as a consequence of the rotary motion ofthe needle cylinder about its own axis. Said cutter is provided with aplurality of teeth and generally rotates at the same speed as the needlecylinder. When a thread guide is raised in order to prevent the needlesfrom engaging the thread and the needles that have engaged said threadare lowered into the needle cylinder, the portion of thread that liesbetween the thread guide and the last needle that engaged said thread isengaged by a tooth of the cutter and is drawn until said tooth of thecutter encounters a fixed abutment or blade, which cuts the thread.

In the region between the thread guide and the blade, above the needlecylinder, within the cylindrical surface traced by the needles, there isan aspirator port. In practice, the portion of thread that lies betweenthe corresponding thread guide and the tooth of the cutter that hasengaged it, before cutting, is placed below the aspirator port, so thatafter cutting the cut end of said thread portion is aspirated into theaspirator port. In this manner, the portion of thread that lies betweenthe thread guide and the cut end is retained and kept tensioned, so thatwhen the corresponding thread guide is lowered again said portion ofthread descends between two contiguous needles, ensuring that saidthread is engaged correctly by the first needle that is moved to knit atthe feed being considered in order to knit with said thread.

When the thread is elastically extensible and is fed in a pre-tensionedcondition, the retention performed by the aspirator port may beinsufficient, and the thread, after cutting, might contract and returntoward the dispensing end of the thread guide due to elastic reaction,to the point of sliding out of said thread guide, making it impossibleto subsequently resume knitting with that thread.

In these cases, and possibly in the case of particular knittingrequirements, downstream of the thread guides of a feed along thedirection of rotation of the needle cylinder with respect to the threadguides there are thread gripping devices, which are designed to performa firmer and more reliable retention of the thread when it is cut.

One of the thread gripping devices currently used in circular knittingmachines or hosiery knitting machines comprises a supporting element,which is fixed to the structure of the machine that supports the threadguides proximate to a feed or drop. Said supporting element supports atleast one elastic lamina element and a thread locking lever, which ispivoted to the supporting element and can rotate in a scissor-likefashion with respect to the elastic lamina element in order to catch thethread directly before it is cut and clamp it between the locking leverand the elastic lamina element.

The locking lever and the elastic lamina element are arranged on planesthat are substantially radial with respect to the needle cylinder andare located above the needle cylinder.

The locking lever has, on its lower side, which faces the upper end ofthe needle cylinder, a lug that forms a shoulder that is directed towardthe axis of the needle cylinder.

In order to grip the thread, the locking lever is turned about its ownpivoting axis, on its plane of arrangement, which lies substantiallyradially with respect to the needle cylinder, so that its lower endmoves transversely to the path of the thread in order to engage saidthread by means of said shoulder and move the thread toward the axis ofthe needle cylinder and grip it between said locking lever and theelastic lamina element.

Assurance of thread grip is entrusted to the correct engagement of thethread by said shoulder.

If, at the end of the thread feeding step and directly before or duringthe rotation of the locking lever meant to catch the thread in order togrip it, the thread moves accidentally toward the axis of the needlecylinder, with the gripping device described above the shoulder of thelocking lever, in its movement toward the axis of the needle cylinder,cannot engage the thread, and therefore the device is unable to grip thethread.

SUMMARY OF THE INVENTION

The aim of the present invention is to solve the problem noted above, byproviding a device for gripping thread in circular hosiery knittingmachines or the like that provides great assurance of thread grip duringthread cutting.

Within this aim, an object of the invention is to provide a device thatensures correct thread grip even if, at the end of the thread feedingstep or during its engagement for gripping, the thread moves abnormallytoward the axis of the needle cylinder.

Another object of the invention is to provide a structurally simpledevice that can be installed on a wide range of circular hosieryknitting machines or the like.

This aim and these and other objects that will become better apparenthereinafter are achieved by a device for gripping thread in circularhosiery knitting machines or the like, comprising a supporting elementthat can be fixed to the structure of the machine that supports thethread guides proximate to a drop or feed, above the needle cylinder andproximate to the needle work area, said supporting element bearing atleast one elastic lamina element that is arranged on a plane that liessubstantially radially with respect to the needle cylinder, saidsupporting element furthermore supporting a thread locking lever that ispivoted to said supporting element with one of its portions and has apivoting axis that is orientated substantially at right angles to theplane of arrangement of said elastic lamina element, said locking leverbeing laterally adjacent to said elastic lamina element and having agrip portion that can engage the thread dispensed by at least one threadguide at the corresponding feed or drop, actuation means being providedfor actuating said locking lever for its scissor-like rotation withrespect to said elastic lamina element about said pivoting axis for thepassage of said locking lever from an inactive position, in which saidthread grip portion is spaced from said elastic lamina element in theopposite direction with respect to the axis of the needle cylinder, toan active position, in which said thread grip portion is closer to saidelastic lamina element and laterally superimposed thereon, in order togrip the thread between said elastic lamina element and said lockinglever, or vice versa, characterized in that said thread grip portion hastwo mutually opposite shoulders that delimit bilaterally the movement ofthe thread toward or away from the axis of the needle cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will becomebetter apparent from the description of a preferred but not exclusiveembodiment of the device according to the invention, illustrated only byway of non-limitative example in the accompanying drawings, wherein:

FIG. 1 is a partially sectional side elevation view of the deviceaccording to the invention, with the locking lever in the activeposition;

FIG. 2 is a view, similar to FIG. 1, of the device according to theinvention, with the locking lever in the inactive position;

FIG. 3 is a sectional view of FIG. 1, taken along the line III—III;

FIG. 4 is an exploded perspective view of the locking lever;

FIG. 5 is a sectional view, similar to FIG. 3, of the device accordingto the invention, applied above the needle cylinder of a circularknitting machine or hosiery knitting machine, which is shown onlyschematically for the sake of simplicity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the figures, the device according to the invention,generally designated by the reference numeral 1, comprises a supportingelement 2, which can be fixed to the structure of the machine thatsupports the thread guides 3, proximate to a drop or feed, above theneedle cylinder 4 and proximate to the needle work area 5.

The supporting element 2 supports at least one elastic lamina element 6a and 6 b, which is arranged on a plane that is substantially radialwith respect to the needle cylinder 4. The supporting element 2 furthersupports a thread locking lever 7, which is pivoted to the supportingelement 2, with one of its portions, about a pivoting axis 7 a, which issubstantially perpendicular to the plane of arrangement of the elasticlamina element 6 a and 6 b.

The locking lever 7 is laterally adjacent to the elastic lamina element6 a and 6 b and has a grip portion 8, which can engage the thread 9dispensed at the corresponding feed or drop of the machine.

The device comprises means 10 for actuating the locking lever 7 in orderto produce its scissor-like rotation, with respect to the elastic laminaelement 6 a and 6 b, about the pivoting axis 7 a for the passage of thelocking lever 7 from an inactive position, shown in FIG. 2, in which thegrip portion 8 of the locking lever 7 is moved away from the elasticlamina element 6 a and 6 b in the opposite direction with respect to theaxis of the needle cylinder 4, to an active position, in which said gripportion 8 is closer to, and laterally superimposed on, the elasticlamina element 6 a and 6 b, in order to grip the thread 9 between theelastic lamina element 6 a and 6 b and the locking lever 7 and viceversa.

According to the invention, the grip portion 8 has two mutually oppositeshoulders 11 a and 11 b, which delimit bilaterally the movement of thethread 9 toward or away from the axis of the needle cylinder 4.

Preferably, instead of a single elastic lamina element, which might beconstituted by the elastic lamina element 6 a, there are two elasticlamina elements 6 a and 6 b, which are arranged side by side and canflex elastically toward or away from each other.

The locking lever 7, in passing from the inactive position to the activeposition, wedges itself at least with the grip portion 8 between thepair of elastic lamina elements 6 a and 6 b.

At least the portion of the locking lever 7 that is meant to wedgeitself between the pair of elastic lamina elements 6 a and 6 b is flat,and at least the region 7 b thereof meant to be the first to penetratebetween the elastic lamina elements 6 a and 6 b in passing from theinactive position to the active position is wedge-shaped.

Conveniently, the side of the pair of elastic lamina elements 6 a and 6b that is directed toward the locking lever 7 in the inactive positionis bent so as to form a guiding flared portion 6 c for the wedging ofthe locking lever 7 between the pair of elastic lamina elements 6 a and6 b.

The device is meant to be mounted above the needle cylinder 4, so thatthe lower side of the locking lever 7, on which the shoulders 11 a and11 b are formed, lies above the circular cutter 12 usually provided incircular knitting machines or hosiery knitting machines, and the elasticlamina elements 6 a and 6 b lie within the cylindrical surface traced bythe needles 5 as a consequence of the rotation of the needle cylinderabout its own axis.

The locking lever 7, in the inactive position shown in FIG. 2, isarranged so that the region located between the shoulders 11 a and 11 blies at the path of the thread 9 at the end of its feeding to theneedles 5 of the machine, as will become better apparent hereinafter.

The rotation of the locking lever 7 about the pivoting axis 7 a, inpassing from the inactive position to the active position or vice versa,occurs on a plane that is substantially radial with respect to theneedle cylinder 4, so that the lower end of the locking lever 7, onwhich the shoulders 11 a and 11 b are formed, moves transversely to thepath followed by the thread 9 during its feeding to the needles 5 of themachine.

Conveniently, the shoulders 11 a and 11 b have an undercut region, whichforms a receptacle for retaining the thread 9 so as to assuredly preventthe thread from exiting from the region of the locking lever 7 that isindeed delimited by the shoulders 11 a and 11 b.

In positioning the device on the machine, the axis 7 a for pivoting thelocking lever 7 to the supporting element 2 is arranged above the regionof mutual lateral overlap of the locking lever 7 with the elastic laminaelements 6 a and 6 b.

The actuation means 10 comprise a pneumatic cylinder 20, which isconnected to, or integrated with, the supporting element 2.

In the illustrated embodiment, the pneumatic cylinder 20 is formeddirectly within the supporting element 2. More particularly, in thesupporting element 2 there is a cylindrical chamber 21, which slidinglyaccommodates a piston 22, which acts on a region of the locking lever 7that lies between the pivoting axis 7 a and the elastic lamina elements6 a and 6 b.

The chamber 21 has an opening that is connected to a supply connector23, which can be connected selectively to a compressed air line or to avent in order to produce the translational motion of the piston 22toward the locking lever 7 or to allow the sliding of the piston 22 inthe opposite direction, in a per se known manner.

The passage of the locking lever 7 from the active position to theinactive position, performed by virtue of the actuation of the pneumaticcylinder 20, is contrasted by elastic means, constituted by a spring 24in which one end is connected to the supporting element 2 and theopposite end is connected to the locking lever 7.

Advantageously, the region 40 of the locking lever 7 that is in contactwith the thread 9 during its gripping is made of a material that has ahigher friction coefficient, in relation to the thread 9 to be gripped,than the remaining part of the locking lever 7.

Conveniently, said material is constituted by an elastically deformablematerial, preferably natural or synthetic rubber.

The region 40 is preferably formed by an insert 41, made of saidmaterial, which is applied to the body of the locking lever 7 at asuitable recess 42 formed in the side of the locking lever 7 thatcooperates with the elastic lamina element 6 a in gripping the thread 9.

The insert 41 protrudes slightly from said side of the locking lever,and its surface that protrudes from the side of the locking lever 7 isconveniently blended with the surface of said side of the locking lever7.

It should be noted that the insert 41 is limited only to the region ofthe locking lever 7 that makes contact with the elastic lamina element 6a when the thread 9 is gripped, so as to limit the extent of the slidingof the insert 41 against the elastic lamina element 6 a and thus limitthe wear of the insert 41.

Preferably, the insert 41 also covers the region in which the shoulder11 a is formed.

According to requirements, the device according to the invention can bearranged proximate to the thread guides 3, as shown, or proximate to thethread aspirator port, if provided, which is usually provided incircular knitting machines for hosiery or the like.

For the sake of completeness in description, it should be noted that thelocking lever 7 has, on the opposite side with respect to its lower end,in which the shoulders 11 a and 11 b are provided, an extension 25 thatprotrudes upward from the supporting element 2 in order to allow, ifrequired, the manual actuation of the locking lever 7.

Furthermore, with reference to FIG. 5, downstream of the thread guides 3along the direction of rotation of the needle cylinder 4 about its ownaxis there is, in a per se known manner, a blade 26 that cooperates withthe teeth of the cutter 12 in cutting the thread 9.

Operation of the device according to the invention is as follows.

During the feeding of the thread 9 to the needles 5, the correspondingthread guide 3 is lowered toward the needles 5 or in any case in aposition that allows the needles 5 of the machine to engage the thread9. In this operating condition, the locking lever 7 can be in the activeposition, shown in FIG. 1, or in the inactive position, shown in FIG. 2.

If the locking lever 7 is in the active position, before the end of thestep for feeding the thread 9, i.e., before lifting the thread guide 3,the locking lever 7 is moved into the inactive position, shown in FIG.2. At the end of the step for feeding the thread 9, the thread guide 3is raised or otherwise moved into a position that prevents the needles 5from engaging the thread, and the thread 9 remains engaged with the lastneedle fed. The portion of thread 9 that lies between the thread guide 3and the last needle that engaged it, as a consequence of the movement ofthe thread guide 3 and of the traction performed by said needle, risesand moves toward the axis of the needle cylinder 4, arranging itself inthe space of the locking lever 7 that is delimited by the shoulders 11 aand 11 b, which limit the possibility of lateral movements of the thread9. In particular, the shoulder 11 b, which is directed away from theaxis of the needle cylinder 4 and is located between the axis of theneedle cylinder 4 and the thread 9, limits, during this step, thepossibility of movement of the thread 9 toward the axis of the needlecylinder 4.

The portion of thread 9 that lies between the thread guide 3 and thelast needle that engaged it is caught by a tooth of the cutter 12, whichgradually draws it toward the blade 26. Just before the thread 9undergoes the cutting action of the blade 26, the pneumatic cylinder 20is discharged, so that by virtue of the action of the spring 24 thelocking lever 7 is rotated about the pivoting axis 7 a, passing from theinactive position to the active position, i.e., moving with its lowerend toward the axis of the needle cylinder 4. As a consequence of thismovement of the locking lever 7, the shoulder 11 a engages the thread 9and draws it between the elastic lamina elements 6 a and 6 b. The thread9 is thus gripped between the locking lever 7 and the elastic laminaelements 6 a and 6 b. In particular, the thread is gripped between theelastic lamina element 6 a and the locking lever 7.

More particularly, the thread 9 is gripped between the region of thelocking lever 7 at which the insert 41 is located and the elastic laminaelement 6 a. By way of the high friction and the deformability ensuredby the insert 41, the thread 9 is retained with absolute assurance evenif the thread 9 is constituted by an elastic thread that has a smalldiameter and is fed in a pre-tensioned condition, and even if theelastic lamina element 6 a is not perfectly parallel to the grip portion8 of the locking lever 7.

When one wishes to resume knitting with the thread retained by thelocking lever 7, the thread guide 3 is moved again into a position thatis suitable to allow the thread 9 to be gripped by the needles 5, andthe locking lever 7 is returned, by way of the actuation of thepneumatic cylinder 20, to the inactive position, in contrast with theaction of the spring 24.

In practice, it has been found that the device according to theinvention fully achieves the intended aim, since by avoiding abnormalmovements of the thread in the direction of the axis of the needlecylinder of the machine during the step in which feeding ends and thethread is engaged, it is capable of gripping the thread with absoluteassurance during its cutting.

Furthermore, thanks to the presence of the insert applied to the lockinglever, one achieves high reliability in the gripping of small-diameterelastic threads.

The device thus conceived is susceptible of numerous modifications andvariations, all of which are within the scope of the appended claims;all the details may further be replaced with other technicallyequivalent elements.

In practice, the materials used, as well as the dimensions, may be anyaccording to requirements and to the state of the art.

The disclosures in Italian Patent Application No. MI2001A002776 fromwhich this application claims priority are incorporated herein byreference.

1. A device for gripping thread in a circular hosiery knitting machineprovided with a structure, a needle cylinder and needles, comprising: asupporting element fixable to the structure and that supporting threadguides proximate to a drop or feed, above the needle cylinder andproximate to the needle work area of the machine, said supportingelement being provided with and bearing at least one elastic laminaelement that is arranged on a plane that lies substantially radiallywith respect to the needle cylinder, and furthermore being provided withand supporting a thread locking lever that is pivoted thereto with aportion thereof, said supporting element having a pivoting axis that isorientated substantially at right angles to a plane of arrangement ofsaid elastic lamina element; said locking lever being laterally adjacentto said elastic lamina element and having a grip portion for engagingthread dispensed by at least one thread guide at a corresponding feed ordrop; actuation means for actuating said locking lever for scissor-likerotation thereof with respect to said elastic lamina element about saidpivoting axis and for passage of said locking lever from an inactiveposition, in which said thread, grip portion is spaced from said elasticlamina element in an opposite direction with respect to an axis of theneedle cylinder, to an active position, in which said thread gripportion is closer to said elastic lamina element and laterallysuperimposed thereon, in order to grip thread between said elasticlamina element and said locking lever, and vice versa, and wherein saidthread grip portion has two mutually opposite shoulders that delimitbilaterally movement of the thread toward or away from the axis of theneedle cylinder.
 2. The device of claim 1, comprising two elastic laminaelements that are arranged side by side and are elastically flexibletoward and away from each other, said locking lever being adapted, uponpassing from said inactive position to said active position, to wedgewith at least said thread grip portion between said pair of elasticlamina elements.
 3. The device of claim 2, wherein at least a portion ofsaid locking lever that wedges between said pair of elastic laminaelements is flat.
 4. The device of claim 2, wherein a portion of saidlocking lever that is adapted to wedge between said pair of elasticlamina elements is wedge-shaped, and wherein a side of said pair ofelastic lamina elements that is directed toward said locking lever insaid inactive position is bent so as to form a flared portion forguiding wedging of said locking lever between said pair of elasticlamina elements.
 5. The device of claim 1, wherein said thread gripportion of said locking lever is formed on a lower side of said lockinglever that faces a top region of the needle cylinder.
 6. The device ofclaim 1, wherein the axis about which said locking lever is pivoted tosaid supporting element is arranged above a region of mutual lateraloverlap of said elastic lamina elements with respect to said lockinglever.
 7. The device of claim 1, wherein said mutually oppositeshoulders have an undercut region that forms a receptacle for retainingthread.
 8. The device of claim 1, comprising elastic return means thatconnect said locking lever to said supporting element, wherein saidactuation means comprising a pneumatic cylinder, which is connected tosaid supporting element and has a piston, said pneumatic cylinder actingwith the piston on a region of said locking lever in order to pass fromsaid active position to said inactive position in contrast with saidelastic return means.
 9. The device of claim 1, wherein a region forgripping the thread between said locking lever and said at least oneelastic lamina element is arranged between the cylindrical surface alongwhich the needles are arranged in the needle cylinder and the axis ofthe needle cylinder.
 10. The device of claim 9, wherein the region ofsaid locking lever that is in contact with the thread during gripping ismade of a material that has a higher friction coefficient, in relationto the thread to be gripped, than the remaining part of said lockinglever.
 11. The device of claim 10, wherein said material is constitutedby an elastically deformable material.
 12. The device of claim 11,wherein said elastically deformable material is constituted by rubber.13. The device of claim 10, wherein said region of the locking leverthat is in contact with the thread during gripping is formed by aninsert that is applied to the body of said locking lever at a recessformed on a side of said locking lever that cooperates with said elasticlamina element in gripping the thread, said insert protruding from saidside of the locking lever.
 14. The device of claim 13, wherein thesurface of said insert that protrudes from said side of the lockinglever is blended with the side of said locking lever.
 15. The device ofclaim 12, wherein said material is limited to the region of said lockinglever that makes contact with said elastic lamina element when thethread is gripped.